1. Field of the Invention
The invention relates in general to a method and a device of displaying a character or characters, and more particularly to a character displaying method and a character displaying device capable of decreasing a memory bandwidth.
2. Description of the Related Art
Due to the flourishing development of the consumer electronic product, the video/audio entertainment product has become an indispensable part in the daily life of the human being. In addition, the changing technology with each passing day has brought the people more and more different enjoyments. For example, the conventional television only can receive the signal transmitted from a wireless television station, and the number of the channels that may be selected by the user is limited. With the popularization of the cable television system, the user can watch the programs in the domestic cable channels as well as abroad television channels so that the options of the users are greatly increased. Recently, a digital television or a setup box with the function of browsing the Internet has been developed in the market in order to provide the user more and more choices.
When a displaying device in the conventional television, the digital television or the setup box is connected to a cable/wireless television channel or Internet, the displaying device receives frames of the television program or the webpage, and represents and displays the characters of the frame one by one in an order from left to right and from top to bottom. During the conventional character displaying process, a central processing unit (CPU) of the displaying device reads bitmap raw data of a first character from a system memory, and then transfers the bitmap raw data to an off-screen memory. Then, a graphic engine chip generates character representing data according to the bitmap raw data of the character in conjunction with a suitable color extension or conversion command, records the character representing data in an on-screen memory, and displays the character representing data on a screen. The above-mentioned steps are repeated until all the characters have been processed and displayed on the screen.
However, the same character has the extremely high repetition rate in the same frame. If the character “a” appears four times in the same frame, the conventional method is to deliver the bit map data of the character “a” from the system memory to the off-screen memory four times. Thus, a lot of memory bandwidths may be occupied so that the system efficiency of the displaying device is greatly reduced. Consequently, how to display all characters of a frame on a screen effectively is a problem to be solved.